1. Field of the Invention
The present invention relates to a thermal transfer material which can be thermally transferred by a thermal medium such as a thermal head, a recording material used in combination with the thermal transfer material, and a thermal transfer recording method using the thermal transfer material and the recording material and, more particularly, to a thermal transfer material, a recording material, and a thermal transfer recording method capable of forming an image with good resistance to a plasticizer, chemical resistance, and mechanical strength.
2. Description of the Prior Art
Heat-sensitive recording systems have been widely used in the fields of a facsimile or various printers because they are of dry type and can perform maintenance free recording. Recently, as an application of these heat-sensitive recording systems, visible information is often recorded on a base other than paper, e.g., a plastic base or information recording card such as a pre-paid card, a sealless pass, a coupon card, or the like. For this purpose, a recorded image must have good resistance to wear, resistance to weather, resistance to water, chemical resistance, and forgery preventive property. In addition, a demand has arisen for a recording system in which information recorded in, e.g., a computer can be easily output and recording can be performed with a mechanically simple arrangement.
Examples of the recording system which can satisfy the above requirements are direct heat-sensitive recording and thermal transfer recording. As the direct heat-sensitive recording, a heat-sensitive medium using a leuco dye is proposed (Japanese Patent Disclosure (Kokai) No. 59-199285) and practiced. However, since the leuco dye is used, reliability of an image after recording is poor, e.g., re-coloring occurs due to heating, discoloration or decoloration occurs due to light incidence, and storage stability over time is degraded. In order to solve these problems, a heat-sensitive recording medium using a metal deposited film is proposed (Japanese Patent Disclosure (Kokai) No. 59-199284). According to this medium, although the above drawbacks are improved, a printing energy is high, and printing requires a long time. In addition, since a recording layer is a metal deposited film, no contrast is obtained between non-image and image portions, and a background has a metallic color, i.e., has no whiteness. For this reason, applications are limited to special purposes. That is, according to the direct heat-sensitive recording type, recording itself has problems, applications are limited, and only mono-color visible information can be obtained because of its recording system. In the thermal transfer recording type, a thermal transfer material consisting of a hot-melt ink layer such as wax is superposed on a recording material obtained by forming a porous ink absorbing layer on a plastic base, thereby performing transferring and printing. In this system, by changing coloring agents of the ink layer of the thermal transfer material, full-color visible information can be printed. However, if an image portion is rubbed by a hand or the like, tailing and contamination occur, thereby degrading reliability of a recorded image. If stability of the recorded image is improved, this system is preferable because applications are not limited, i.e., it can be used in a variety of fields.